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Adcom 5400 amplifier blowing all fuses

Discussion in 'Audio' started by Audiofreak1, Sep 20, 2018.

  1. VenomBallistics

    VenomBallistics

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    Aug 30, 2018
    that describes a power supply issue.
     
    Audiofreak1 likes this.
  2. Audiofreak1

    Audiofreak1

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    Sep 20, 2018
    Well I pulled the power supply board. I checked and replaced the remaining electrolodic caps on board removed the big power caps tested and they passed tested fine. Checked over everything and resoldered where needed. Clean up the ground connect on the board has a rust on it may have been the culprit of this humm I spoke of. Used dim bulb tested everything checked good. So removed that from equation. Next I tested the bios of both side 41mv left 38 right. Then checked dc offset left 13.9 right 10.7 so it all checked out. Now plugged a speaker in to each channels no hum all quiet. Played cd turned it up some played fine! No sound or noises during the playing season 2 hrs. Also readjusted the bios first then offset and sound good. Only thing is power switch on power on I get a small pop not bad. And also at about 1030 of the dial of pre amp I am getting the distortion lights. I never checked the protection board might have to here. When it was working before I never got those light. Now it does seem to be playing a little louder than I think it did before. Maybe just me but I still think something is going on somewhere. Now I just check the amps ground floor no music just turned the volume up. And right side there’s is a air noise coming out of tweeter and a low almost not noticeable hum in the woofer. The left side has a hum in the tweeter and the woofer a little louder than the right side. Neither are noticeable unless you put your ear up to speaker. If you have any input on where to look now I would appreciate it. I am going to check the protection board here tomarrow night so will see if anything’s a miss
     
  3. VenomBallistics

    VenomBallistics

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    Aug 30, 2018
    Signal in and signal out ... that's excellent.
    If the thing can track well enough to reproduce a signal, the active components are good. There could still be a sketchy cap in there, but nothing to warrant gutting it. I think it'll be a function of tuning now
     
    Audiofreak1 likes this.
  4. Audiofreak1

    Audiofreak1

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    Sep 20, 2018
    I have a question for you I need to find the component that controls the signal in the amp. It is getting too loud to fast does not match my other amps. So I ether put a pot on each channel or I find the culprit and fix it. Maybe a resistor? Any help will help in the end to get me a better night sleep. Had a dream I was using it and it blew up like a Granade lol. Anyway let me know if possible. Now there are two caps on the board that I put I. That are close but not the same as the old ones. Made a mistake going off scamatics :(. The caps are c609 &c610 was a 4.7 25v I replaced with 4.7 50v. The other one is c617 c618 original was 100uf 25v I replaced with 100uf 16v. Would either of those be doing it?
     
    Last edited: Oct 30, 2018
  5. VenomBallistics

    VenomBallistics

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    Aug 30, 2018
    so its kinda "ticklish" .... Engineering from thin air, this would prompt a revisit to the NFB loop.
    Essentially, a power amp is an Op amp on a much larger scale. You'd do well to study them a bit, even try to scratch build a few projects out of them like preamps and the like.

    one of the basic rules is that the Op Amp will try to keep the voltage at the - input the same as the voltage of the + input at any given moment.
    It achieves this through a voltage divider that feeds a fraction of the signal from the output to the - input.
    R608 and R610 are part of this loop. the rest of it ties to ground to establish a ratio.
    Look at these for signs of overheat first ... if not, Im going to assume damage due to reverse voltage from your oops early on.
    At which point, Just start replacing transistors.
     
  6. VenomBallistics

    VenomBallistics

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    Aug 30, 2018
    the 4.7μ 25V should be alright ... the 100μ 16V ... umm no ... replace with same or higher voltage rating (within reason)
     
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  7. Audiofreak1

    Audiofreak1

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    Sep 20, 2018
    Ok I am going to replace that one cap with a higher voltage cap. I moved the amp over to my system and plugged it into my yamaha c4 pre amp and it works fine. Volume matches the other speakers good! I had it on a Yamaha Rx 690 a/v receiver and was using the front pre outs on it. They must be set higher or something. I kinda had a gut feeling on that and sure enuf that was the problem. So amp is stable.
     
  8. VenomBallistics

    VenomBallistics

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    Aug 30, 2018
    outstanding .... change out that sub value cap ASAP and it should give good service for the duration
     
    Audiofreak1 likes this.
  9. Audiofreak1

    Audiofreak1

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    Sep 20, 2018
    Yeah I will not sure why the scamatics for the amp have it as a 16v cap. I will be replacing it with a 25v cap elna smel
    i am not sure why they put that the part was 16v cap in scamaticsparts list. I am going to put a 25v there elna silmic ll cap in there. I wanted to ask I am not sure if you know a lot about audio electronics meaning parts to use to get better sound cap wise. I picked the silmic elna caps seem to sound good. Wonder if you know of any that are better or if I made a good choice on the caps?
     
  10. VenomBallistics

    VenomBallistics

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    Aug 30, 2018
    Its a well known debate in audiophile circles as to what cap, transistor, tube, cable ect ect sounds best.
    It is a magical land filled with pixies, unicorns and things crafted at the hands of elven masters where wonders rain from the skys dazzling all with awesome creations ....
    Over here where the electrons meet the various elements, we've slain the elves, and drank the blood of the unicorns. We've slaughtered all the dragons and mailed the pixies spines to their mothers.
    There aint no magic left.
    That said ... Design of the equipment is the main contributor to the end result.
    You will probably tell the difference between an LM386 amp and your Adcom in very short order. but two Adcoms running speakers through oxygen free Monster cable and coat hangers ... you won't hear the difference.
    Even less so between capacitors.
    If I am building, I look at aspects that have an impact on longevity. I might use 1/2 watt resistors where 1/4 watt will do, Higher VA transformer, Service life figures on caps. It's the design in which they are utilized that will have some impact on the sound quality.
    Don't get me wrong, I encourage exploration and experimentation, but I do laugh at some of the audiophiles that bicker over specific name brands and even series and lot numbers of components.
     
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  11. Audiofreak1

    Audiofreak1

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    Sep 20, 2018
    Yeah I agree there are to many capacitors out there. So many it can make the novice confused and fall off his dragon. Anyway I have personally put the elna silmic ll Cap’s and from what I can hear it is pleasentrys to my ears. Wine flowing and flowers blooming sip sip. Honestly though I feel the on a mosfet I am getting really good sound from these. Not to mention all the power caps are replaced also. Not one single old electrolodic. And yes I agree there are a lot of silly folk that will swear that anything gold silver and shiny will make there speakers sound better. Now that that said,I truly like the warm extended highs I hear with the elna silmic 2 they are by far the cheapest best sounding cap for money. I am not saying that there are not better or 24k gold caps that are out there lol.
    And yes you are right keeping a buffer between the component and the life is good. Up the size a bit And longer lasting they will be. Wise with the cap I am! You 100% right bet you don’t hear that everyday haha. My wife love to hear that :). And I am not a fan of monster capable and I know it was a exzample but there to main stream and I think the quality has dropped. Sewell make a good cable and banana connecter, cheaper and just as good if not better. You said I won’t hear difference but I beg to differ on that not saying it was night and day but music got tighter and the highs seem to be extended more. But I had a few bad cap so duh you will notice that. If I bought two adcoms new and change the one to the silmic caps and other leave factory there might be a slight difference but not much. So depends on how old the caps are and if leakage is happing which in my case a few were.
    I will never hook up a bridge rectifier wrong again that goes for anything anymore. Check check check check and check etc. then get here ready to turn on check again and again we’ll you get the idea. I got lucky I did not hurt something more than I did.
     
  12. VenomBallistics

    VenomBallistics

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    Aug 30, 2018
    yeah ... lots of measure once cut twice .... then buy a new one happens.
    Depending upon how far down the audio rabbit hole you have gone, you might like the G Randy Sloan High Power Amp book. Especially if you have some big transformers in dead gear.
    While I kinda like some of the self preservation engineering in your Adcom, some of the Sloan designs are capable of making it look like a toy. Where yours employs a single differential input, some of the more advanced Sloan designs run symmetrical setups with interesting options and power figures well beyond your 125W Adcom. Its just a matter of having the iron to run them.
    one thing I have observed in his design approach is that they all rely on a relatively small selection of active parts that get engineered into a comprehensive array of designs.
    Its not so much the parts used, its how you use the parts.

    For A vs B comparisons, you really need a twin setup.
    two complete systems where the variable can make a difference without time to allow your memory to play a part.
    Its just not fair to try sample B after a tinker session.
    Yeah .. you might actually hear some difference between capacitors ... however, that difference will almost always be age related.
    It might be worth it for you to build a pair of amps around a healthy IC for some scaled down abuse / fry and try testing.
    Off the cuff, this should fit the bill.
    https://www.digikey.com/product-detail/en/texas-instruments/LM3886TF-NOPB/LM3886TF-NOPB-ND/263599

    You could probably build a dummy load from an RDA from a vape shop for endurance runs without going deaf.
     
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